1. Field of the Invention
This invention relates to novel security articles comprising fibers, threads and fiber sections (“dots”) possessing multiple verification characteristics. The fibers possess unique and difficulty duplicated combinations of complex cross-sections, components, and multiple luminescent responses. The many verifiable characteristics of the security fibers, threads, and dots provide high levels of protection against fraudulent duplication of articles in which they are incorporated. The manifold security features provide means of tailoring specific identity characteristics for specific use and users.
2. Description of the Related Art
Security fibers are fibers incorporated in fiduciary documents or other articles for the purpose of ensuring identification, authentication, and protection against forgery, imitation or falsification. The term “security thread” has been employed to describe twisted or braided fibers or strips of films for the same purposes.
German Patent 19802588 describes cellulose fibers containing luminescent additives for security purposes.
European Patent 066854 B1 describes cellulose acetate security fibers and security papers containing the fibers. The security fibers are spun from an acetone solution containing a lanthanide chelate. The fibers are colorless under normal lighting but show narrow-band emission in the visible or infra-red (IR) when excited by ultraviolet (UV) light. A security thread twined of fibers having different luminophors is described wherein coded information is impressed on the security thread.
U.S. Pat. Nos. 4,655,788 and 4,921,280 describe security fibers invisible in sunlight or artificial light, which under excitation by IR, UV or x-rays, exhibit a luminescence. The security fibers are prepared by a process of dyeing conventional textile fibers such as polyester, polyamide and cellulosic fibers with rare earth chelates.
German Patent DE-A 14 46 851 describes a security thread having a microprint executed in several colors.
U.S. Pat. No. 4,897,300 describes a security thread having luminescent colors that are invisible in normal lighting and are provided along the security thread in successive and overlapping portions which, when the colors are excited, have a length recognizable to the naked eye and in the overlapping areas have characteristic mixed luminescences. The security threads are produced by printing strip shapes on flat sheets and then cutting them up.
U.S. Pat. No. 6,068,895 describes a woven security label incorporating a detectable filament made by adding about 20 weight percent (wt. %) of an inorganic fluorescent substance to polyester dope and spinning filaments out of the dope.
U.S. Pat. No. 4,183,989 describes a security paper having at least two machine verifiable security features, one of which is a magnetic material, and a second of which may be a luminescent material. The luminescent material is dispersed in a lacquer and coated onto a film. The film is divided into planchettes of approximately 1 mm diameter and incorporated in the paper.
Korean Patent KR 9611906 and WO 9945200 describe methods of preparing luminescent fibers by dyeing. Korean Patent KR 9611906 describes the incorporation of the fibers into paper material.
UK Res. Discl. (1998), 411 (July), P. 877–P. 878, discloses bi-component fibers with differentially dyeable domains for incorporation into security papers.
Chinese Patent No. CN 1092119 describes polyvinyl alcohol fibers of 1–10 mm length containing pigments, dyes and fluorescent materials.
U.S. Pat. Nos. 5,876,068, 5,990,197, 5,990,930 and 6,099,930 describe yet other means of providing security elements involving luminescent substances.
In a related area, British Patent 1,569,283 describes an apparatus for verifying the authenticity of documents coded with fluorescent substances.
Each of these patents represented improvements in the state of their respective arts. However, as security technology has evolved, parallel improvements have taken place in the capabilities of those who would evade security measures. A need exists for security fibers possessing unique and more difficulty duplicated combinations of verifiable security characteristics. A further need exists for means to tailor specific identity characteristics for specific users.
Luminescent substances have also been incorporated into fibers for purposes unrelated to security applications or for unspecified purposes.
U.S. Pat. No. 4,781,647 describes a method of producing phosphorescent filaments by mixing phosphors, preferably zinc, cadmium or calcium sulfide into the polymer together with a coupling agent prior to extrusion and spinning into fibers for dolls' hair.
U.S. Pat. No. 5,321,069 describes a process for producing phosphorescent bulked continuous filament (BCF) yarns of thermoplastic polymers for textile applications by melt spinning. The process comprises the steps of mixing the polymer pellets with a wetting agent, preferably mineral oil, adding a phosphorescent powder such as zinc sulfide to substantially uniformly coat the pellets, and heating in an extruder to form and extrude a melt whereby a uniform distribution of phosphorescent pigment is said to be obtained throughout the filaments. The individual filaments may be solid or hollow and may have any conventional shape.
U.S. Pat. No. 5,674,437 describes a method for preparing luminescent fibers comprising the steps of combining in an extruder a thermoplastic polymer with a luminescent metal aluminate pigment, heating and mixing to melt the polymer, and extruding the melt to form a fiber.
U.S. Pat. No. 3,668,189 describes fiber forming fluorescent polycarbonamides prepared by co-polymerization of a fused ring polynuclear aromatic hydrocarbon moiety having at least three fused rings.
Japanese Patents 7300722 A2 and 2000096349 A2 describe sheath-core fibers with the core containing the luminescent substance.